Poly(arylene) having a structure that aromatic rings are serially bound, particularly poly(arylene) having serially .pi. conjugated system along the main chain (for example, poly(p-phenylene), poly(2,5-thienylene), and poly(1,4-naphthalenediyl)) generally possess excellent heat resistance. Further, it is known that addition products of these poly(arylene) to electron acceptors (e.g., AsF.sub.5, etc.) or electron donors (e.g., lithium, sodium, etc.) have conductivity and have property to change their color reversibly (electrochromic) by electrochemical oxidation-reduction so as to be available as materials for displays (for example, High polymers, Japan 38, 1080 (1989)). Japanese Patent Application Laid-Open No.Hei 1-210420 discloses conductive substances produced by reducing polymers having serial .pi. conjugated system along the main chain and groups composed of 6-membered heterocyclic ring units, for example, a 2,5-pyridinediyl group as a repeating constitutive unit. Japanese Patent Application Laid-Open No.Hei 5-70565 discloses poly(quinolinediyl) and poly(isoquinolinediyl), which are composed of condensed heterocyclic ring units and Japanese Patent Application No. Hei 6-56972 discloses quaternary poly(quinolinediyl) and poly(isoquinolinediyl).
However, most of the poly(arylene)s conventionally proposed show low solubility in water or organic solvents and are not melted, which restricts their application and is an obstacle to elicit their characteristic functions. With respect to the above-described poly(arylene)s, it has been desired to modify the molecular structure so as to develop such substances as having properties different from the conventionally known poly(arylene)s. For example, if it is possible to obtain poly(arylene) that has oxidation-reduction potential or changes its color (electrochromic phenomenon), different from the known poly(arylene)s, it would be used as an electrode to provide an electrochromic display which has characteristics different from the conventionally used electrochromic indicative material (for example, "OYO BUTURI", Vol.56, 1433 (1987)) or it would be used as an active material or an electrode to provide a polymer battery that has characteristics different from the known polymer battery (for example, "Denki Kagaku (Journal of the Electrochemical Society of Japan)" 54, 306 (1986)). In order to confer conductivity on poly(arylene)s, it is necessary to effect oxidation (p-doping) or reduction (n-doping) of poly(arylene)s that are usually in a neutral state (cf. the above-described portions of OYO BUTURI and Denki Kagaku (Journal of the Electrochemical Society of Japan)). This oxidation-reduction is disadvantageous in that a corrosive oxidizing agent such as iodine is used, that the process is complicated, and that dopants such as I.sup.-, ClO.sub.4.sup.-, or NR.sub.4.sup.+ may possibly render poly(arylene), which becomes conductive, chemically and physically unstable. Accordingly, it has been desired to develop materials made of poly(arylene)s or its derivatives having no such a dopant and showing conductivity by themselves.